1. Field of the Invention
This invention relates to a rotary head type recording or reproducing apparatus and, in particular, to an apparatus in which a recording medium is rewound while tracing the recording medium with rotary heads.
2. Description of the Related Art
Conventionally, the tape path of a video tape recorder (VTR) using a standard-diameter drum, i.e., of a two-head helical scan VTR, in which the tape is wound around the drum over an angular range of 180.degree. or more, has been provided with a relatively large degree of flexibility in regard to its size and space. This large degree of freedom has made it possible to keep the tape winding angle as small as possible with respect to the guide posts for guiding the tape and to leave a space of some extent between the drum and the guide posts.
FIG. 1 shows an example of the tape path of a conventional VTR of this type. The VTR shown includes a standard rotating drum 1 having a plurality of rotary heads, a tape housing cassette 2, a tape 3, a tension post 4 for controlling the tape tension, and guide posts 5, 6, 7, 8, 9 and 11 for guiding the tape. The reference numeral 10 indicates a capstan, against which a pinch roller 12 is pressed with the tape 3 sandwiched therebetween, which is adapted to transport the tape 3 in a longitudinal direction thereof. During normal recording or reproduction, the drum 1 rotates in the direction indicated by an arrow 13, and the tape 3 runs in the direction indicated by an arrow 14. Thus, the running of the tape and the tracing of the same by the rotary heads are effected substantially in the same direction, although their track inclination angles with respect to the longitudinal direction of the tape differ from each other.
When rewinding the tape at a high speed, the rotating direction of the capstan 10 is reversed, the tape being transported from a take-up reel 16 and taken up by a supply reel 15.
Now, with a view to reducing the size and weight of VTRs, a VTR having a small-diameter drum has recently been produced on a commercial basis. In this VTR, the drum diameter is 2/3, and the tape winding angle with which it is wound around the drum is 3/2, in comparison to the prior art. The drum of this VTR is equipped with four rotary heads exhibiting a phase difference of 90.degree. with respect to each other.
In a VTR using such a small diameter drum, the number of guide posts arranged between the supply reel and the capstan is inevitably large, so that tension loss due to the guide posts cannot be avoided. In addition, since the tape is wound around the drum over a wide angular range, the guide posts are arranged very close to the small diameter drum, the gap secured between them being as small as about 0.1 to 0.2 mm. As a result, it is difficult for the tape to run in a stable manner. Moreover, since the tape is wound around the drum over a wide angular range in a small diameter, the amount of air film on the drum is smaller in comparison to that of the above-mentioned usual drum.
In the case of a VTR employing a standard-diameter drum as described above, the tape winding angle on the drum is not so large, and an air lubricating layer, i.e., a so-called air film, is formed to a sufficient degree between the rotating drum and the tape. In addition, the winding angle around the guide posts is relatively small, so that the tape can be taken up by the supply reel.
However, in the case of a VTR using a small-diameter drum as described above, a problem occurs when rewinding the tape at a high speed by reversing the capstan: namely, it is very difficult for the tape transported by the capstan to be taken up in the normal manner by the supply reel.
That is, the tape becomes loose between the capstan and the drum, which makes it likely that the tape will be damaged. This tendency is particularly conspicuous in a tape which has been used for a long time. Any damage in the tape edge section results in an increased tension loss on the guide posts and the drum, causing an excessively defective take-up of the tape.